Micro-fluid ejection devices continue to be used in a wide variety of applications, including ink jet printers, medical delivery devices, micro-coolers and the like. Of the uses, ink jet printers provide, by far, the most common use of micro-fluid ejection devices. Ink jet printers are typically more versatile than laser printers for some applications. As the capabilities of ink jet printers are increased to provide higher quality images at increased printing rates, fluid ejection heads, which are the primary printing components of ink jet printers, continue to evolve and become more complex.
Improved print quality requires that the ejection heads provide an increased number of ink droplets. At the same time, there is a need to reduce the size of such ejection heads. For some applications, such as color ink jet printing, it is beneficial to have a multi-function ejection head. Such multi-function head may include multiple fluid supply slots for ejecting different fluids, for example, different color inks. Each of the fluids or inks may have different flow characteristics. Accordingly, the fluid supply slots for different fluids typically have different widths.
The manufacture of multiple slots having different widths in a semiconductor substrate is difficult to achieve during a reactive ion etching process. Fluid supply slots having drastically different widths exhibit drastically different etch characteristics, affecting both etch rate and etch profile. Typically, the wider the feature etched in a semiconductor substrate, the faster the etch rate and the more re-entrant the wall angle of the feature. Accordingly, fluid supply slots having larger widths are finished etching before narrower fluid supply slots. The larger the size disparity between the fluid supply slot widths, the more severe the disparity in etch rates and etch profiles. For example, a black ink may require a fluid supply slot having a width of 350 microns, whereas fluid supply slots for cyan, magenta, and yellow inks may have a width of 210 microns. Such a wide disparity is fluid supply slot widths makes simultaneous etching of such fluid supply slots extremely difficult.
With regard to the above, there continues to be a need for smaller ejection heads having increased functionality and improved processes for making micro-fluid ejection heads.